If it already weighs only 7lbs, there's no way 2 lbs can be shaved off it - the only 5lb CF BA factory rifles I'm aware of is a NULA. or a Weatherby UltraLite (in standard cals), but LW customs can be had from Rifles, Inc or Christiansen Arms.

FWIW, Weaver 2-piece bases are about the lightest around, and even WallyWorld sells alloy rings to fit them.

"Some" BA rifles can be run w/o the sheet metal magazine well liner (not very heavy, but still weighing something )- unless your rifle has a detachable mag (you haven't given a complete description, as yet).